Effect of the anodization voltage on the dimensions and photoactivity of titania nanotubes arrays

This work compares the behaviors of TiO2 nanotube (TNTs) array obtained by anodization of Ti foils in an ethylene glycol/NH4F/water electrolyte with different applied voltages during a constant anodization time, and for the same electrolyte composition. The crystal structure and surface morphology of the annealed anodic films are investigated by X-Ray diffraction system, Raman spectroscopy and scanning electron microscopy, respectively. The TiO2 nanotubes obtained at potentials of 20-40-60V show different inner diameters (42-89-124nm), tube length (1.2-3.3-12.7 mu m) and wall thicknesses (12-15-18nm). The influence of these geometric parameters on the photoelectrochemical properties and the photocatalytic activity were investigated in detail. The results showed that the photocatalytic performances of TNT films are improved when the specific surface, the tube length and the solid fraction are increased, but the increase is slowed down when a limiting thickness of the layer is reached. The surface states which usually show high density in nanostructured layers do not seem to influence significantly the photocatalytic activity of the layers. Copyright (c) 2013 John Wiley & Sons, Ltd.